348 research outputs found

    Dispersion of longitudinal momentum distributions induced in fragmentation reactions

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    On the basis of systematic measurements of fragmentation reactions, which provide a detailed overview on the velocity distributions of residual nuclei, an improved description of the kinematical properties of the fragmentation residues is established. This work is dedicated to the fluctuations of their momentum distributions. In contrast to previous investigations, limited to close-to-projectile fragments, we extended our study to the entire production range, down to the lightest observed fragments. In this context, beside the contribution of abrasion and evaporation processes, we considered the effect of the thermal break-up on the width of the momentum distributions. Using approximated theoretical descriptions of the different reaction stages, a new analytical formula for the variance of the momentum distribution is derived, which is well adapted to technical applications.Comment: 14 pages, 3 figures, background info. at http://www-wnt.gsi.de/charms

    Systematic investigation of the isotopic distributions measured in the fragmentation of 124Xe^{124}Xe and 136Xe^{136}Xe projectiles

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    Nuclear expansion and symmetry energy of hot nuclei

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    The decrease in the symmetry energy of hot nuclei populated in 58^{58}Ni + 58^{58}Ni, 58^{58}Fe + 58^{58}Ni and 58^{58}Fe + 58^{58}Fe reactions at beam energies of 30, 40, and 47 MeV/nucleon, as a function of excitation energy is studied. It is observed that this decrease is mainly a consequence of increasing expansion or decreasing density rather than the increasing temperature. The results are in good agreement with the recently reported microscopic calculation based on the Thomas-Fermi approach. An empirical relation to study the symmetry energy of finite nuclei in various mass region is proposed.Comment: 10 pages, 2 figure

    Production of medium-mass neutron-rich nuclei in reactions induced by 136Xe projectiles at 1 A GeV on a beryllium target

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    Production cross sections of medium-mass neutron-rich nuclei obtained in the fragmentation of 136Xe projectiles at 1 A GeV have been measured with the FRagment Separator (FRS) at GSI. 125Pd was identified for the first time. The measured cross sections are compared to 238U fission yields and model calculations in order to determine the optimum reaction mechanism to extend the limits of the chart of the nuclides around the r-process waiting point at N=82.Comment: 9 pages, 6 figure
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